Method for producing transparent conducting film

ABSTRACT

Provided is a transparent conducting film having a favorable optical property, favorable electrical property, and almost no in-plane resistance anisotropy. A method for producing a transparent conducting film provided with a conducting layer containing a metal nanowire and a binder resin, comprises steps of: preparing a coating liquid containing the metal nanowire and the binder resin, and coating the coating liquid on one main face of a transparent substrate, wherein, in the coating step, a bar-coat printing method is performed using a bar provided with a groove having a pitch (P) and a depth (H) which satisfy a ratio P/H of 5 to 30.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2020/021401 filed May 29, 2020, claiming priority based onJapanese Patent Application No. 2019-102654 filed May 31, 2019 and2019-202446 filed Nov. 7, 2019.

TECHNICAL FIELD

The present disclosure relates to a method for producing a transparentconducting film. In more detail, the present disclosure relates to amethod for producing a transparent conducting film containing metalnanowires, by a bar-coat printing method.

BACKGROUND ART

A transparent conducting film is used in various fields, such as aliquid crystal display (LCD), a plasma display panel (PDP), an organicelectroluminescence display, a transparent electrode for a photovoltaiccell (PV) and a touch panel (TP), an electrostatic discharge (ESD) film,electromagnetic interference (EMI) film, and the like. For suchtransparent conducting films, conventionally, films using ITO (indiumtin oxide) have been used.

Recently, touch panels are adopted for smartphones, car navigationsystems, vending machines, etc. In particular, since a foldablesmartphone attracts attention, there is a desire for a foldable touchpanel.

In order to achieve a foldable touch panel, a foldable transparentconducting film, that is, a transparent conducting film having asuperior durability of folding is necessary. Therefore, a metal nanowirefilm has been developed as a transparent conducting film for the nextgeneration.

Patent Document 1 discloses a method for producing a transparentconducting film using a slot die coater having a slot die in the silvernanowire ink coating step. In order to solve the in-plane resistanceanisotropy, a shear velocity (printing speed/gap between a slot die headtip and a film) is specified. However, the printing speed is restrictedby the ability of a production equipment (in particular, a dryingequipment).

Patent Document 2 discloses a slot die coater as a coater using insilver nanowire ink coating step, and discloses that, in order to solvethe in-plane resistance anisotropy, blowing air to the substrate in adirection different from the printing direction, during the drying step,is effective. However, an equipment for blowing air from the differentdirection is additionally required.

Patent Document 3 discloses gravure printing as a silver nanowire inkcoating step, but fails to disclose or suggest a solution for thein-plane resistance anisotropy.

PRIOR ARTS Patent Document

Patent Document 1: Japanese Unexamined Patent Publication (Kokai) No.2011-090879

Patent Document 2: WO 2013/121556 pamphlet

Patent Document 3: Japanese Unexamined Patent Publication (Kokai) No.2014-507746

SUMMARY

In the production of transparent conducting films using metal nanowireink, there are drawbacks that the resistance value (R_(MD)) in theprinting direction is different from the resistance value (R_(TD)) inthe direction perpendicular to the printing direction, that is,anisotropy occurs.

One of the objectives of the present disclosure is to provide atransparent conducting film having a superior optical property and asuperior electrical property, as well as a small in-plane resistanceanisotropy.

The present disclosure includes the following aspects.

[1] A method for producing a transparent conducting film provided with aconducting layer containing a metal nanowire and a binder resin,comprising steps of preparing a coating liquid containing the metalnanowire and the binder resin, and coating the coating liquid on onemain face of a transparent substrate, wherein, in the coating step, abar-coat printing method is performed using a bar provided with a groovehaving a pitch (P) and a depth (H) which satisfy a ratio P/H of 5 to 30.

[2] A method for producing a transparent conducting film according to[1], wherein a material forming a surface of the bar has a frictioncoefficient of 0.05 to 0.45.

[3] A method for producing a transparent conducting film according to[2], wherein, when the coating liquid is coated on one main face of thetransparent substrate, a relative moving velocity (coating velocity) V(mm/sec) of the transparent substrate relative to the bar satisfies2000≥V≥350.

[4] A method for producing a transparent conducting film according to[1], wherein a material forming a surface of the bar has a frictioncoefficient of 0.05 to 0.40.

[5] A method for producing a transparent conducting film according to[4], wherein, when the coating liquid is coated on one main face of thetransparent substrate, a relative moving velocity (coating velocity) V(mm/sec) of the transparent substrate relative to the bar satisfies2000≥V≥50.

[6] A method for producing a transparent conducting film according toany one of [1] to [5], wherein when a groove formed on the bar has apitch (P) and a depth (H), a ratio P/H is 9 to 30.

[7] A method for producing a transparent conducting film according toany one of [1] to [6], wherein the metal nanowire has an average lengthof 1 to 100 μm and an average diameter of 1 to 500 nm.

[8] A method for producing a transparent conducting film according toany one of [1] to [7], wherein the coating liquid has a viscosity in arange of 1 to 50 mPa·s.

In a method for producing a transparent conducting film according to thepresent disclosure, a coating liquid containing a metal nanowire and abinder resin is printed by a bar-coat printing method, and thereby, atransparent conducting film having small in-plane resistance anisotropycan be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A, 1B and 1C are schematic views explaining a shape of a grooveformed on a bar used in a bar coater.

FIGS. 2A and 2B are explanatory views showing a method for measuring aresistance value.

ASPECT OF DISCLOSURE

Hereinbelow, aspects of the present disclosure (hereinbelow, referred toas aspects) will be explained.

A method for producing a transparent conducting film according to thepresent aspect comprises steps of preparing a coating liquid containinga metal nanowire and a binder resin, and coating the coating liquid onone main face of a transparent substrate (transparent film), wherein, inthe coating step, a bar-coat printing method using a bar provided with agroove is used, the groove having a pitch (P) and a depth (H) and aratio P/H being 5 to 30. By the above method for producing a transparentconducting film, a transparent conducting film having a transparentsubstrate provided thereon with a conducting layer containing the metalnanowire and the binder resin, can be produced.

Further, a protection film mentioned below can be formed on atransparent conducting film produced by the above method for producing atransparent conducting film

<Transparent Substrate>

The above transparent substrate may be colored, but having higher totallight transmittance (transparency to visible light) is preferable, and apreferable total light transmittance is 80% or more. For example, aresin film such as polyester (polyethylene terephthalate [PET],polyethylene naphthalate [PEN], etc.), polycarbonate, acrylic resin(poly methyl methacrylate [PMMA], etc.), cyclo olefin polymer, and thelike may be preferably used. As far as the optical property, electricproperty, and durability of folding is not damaged, the transparentsubstrate may be provided with a single or a plurality of layers havingfunctions of easy adhesion, optical adjustment (antiglare,antireflection, etc.), hard coating, and the like, on one or both of themain faces of the transparent substrate. Among these resin films, inview of a superior light transmittance(transparency), flexibility, and amechanical property, using polyethylene terephthalate, a cyclo olefinpolymer is preferable. For polyethylene terephthalate, COSMOSHINE(registered trademark, manufactured by Toyobo Co., Ltd.) can be used.For the cyclo olefin polymer, a hydrogenated ring-opening metathesispolymerization type cyclo olefin polymer of norbornene (ZEONOR(registered trademark, manufactured by Zeon Corporation), ZEONEX(registered trademark, manufactured by Zeon Corporation), ARTON(registered trademark, manufactured by JSR Corporation), etc.) and anorbornene/ethylene addition copolymerization type cyclo olefin polymer(APEL (registered trademark, manufactured by Mitsui Chemicals, Inc.),TOPAS (registered trademark, manufactured by Polyplastics Co., Ltd.))can be used. Specific examples include COSMOSHINE A4100, A4160, andZEONOR ZF-14, ZF-16, ARTON RX4500, RH4900, R5000. The thickness of thetransparent substrate may vary depending on the use thereof, butpreferably, a thickness of 10 to 200 μm is used. In the presentspecification, the term “transparent” refers to a total lighttransmittance of 70% or higher.

<Metal Nanowire>

As a conductive material constituting the conducting layer formed on thetransparent substrate, using metal nanowires is preferable. The metalnanowire is metal having a diameter in the order of nanometer, and is aconductive material having a wire shape. In the present aspect, togetherwith (mixing with) the metal nanowires, or instead of the metalnanowires, a metal nanotube which is a conductive material having aporous or nonporous tubular shape can be used. In the presentspecification, both the “wire” shape and the “tubular” shape refer to alinear shape, and the former is not hollow, whereas the latter ishollow. They may be soft or rigid. The former is referred to as “metalnanowire in a narrow sense”, and the latter is referred to as “metalnanotube in a narrow sense”. Hereinbelow, in the present specification,“metal nanowire” is used to include both the metal nanowire in a narrowsense and the metal nanotube in the narrow sense. Either the metalnanowire in a narrow sense or the metal nanotube in a narrow sense maybe used solely, but they may be mixed.

In the present specification, the “conducting layer” refers to a layerin the shape of a thin film including the above metal nanowires and thebelow-mentioned binder resin, with a thickness of in the range of 20 to200 nm, but is not limited to the layer having a uniform thickness.

As a method for producing the metal nanowire, a known method may beapplied. For example, silver nanowires may be synthesized by reducingthe silver nitrate under the presence of polyvinylpyrrolidone, using apoly-ol method (refer to Chem. Mater., 2002, 14, 4736). Similarly, goldnanowires may be synthesized by reducing the gold chloride acid hydrateunder the presence of polyvinylpyrrolidone (refer to J. Am. Chem. Soc.,2007, 129, 1733). WO 2008/073143 pamphlet and WO 2008/046058 pamphlethave detailed description regarding the technology of large scalesynthesis and purification of silver nanowires and gold nanowires. Goldnanotubes having a porous structure may be synthesized by using silvernanowires as templates, and reducing a gold chloride acid solution. Thesilver nanowires used as templates are dissolved in the solution byoxidation-reduction reaction with the gold chloride acid, and as aresult, gold nanotubes having a porous structure can be produced (referto J. Am. Chem. Soc., 2004, 126, 3892-3901).

The metal nanowires have an average diameter size (average diameter) ofpreferably 1 to 500 nm, more preferably 5 to 200 nm, still morepreferably 5 to 100 nm, and particularly preferably 10 to 50 nm. Themetal nanowires have an average major axis length (average length) ofpreferably 1 to 100 μm, more preferably 1 to 80 μm, still morepreferably 2 to 70 μm, and particularly preferably 5 to 50 μm. Whilesatisfying the above ranges of the average diameter size and the averagemajor axis length, the metal nanowires have an average aspect ratio ofpreferably more than 5, more preferably 10 or more, still morepreferably 100 or more, and particularly preferably 200 or more. Here,the aspect ratio refers to a value obtained by a/b, wherein “b”represents an average diameter size of the metal nanowire and “a”represents an average major axis length thereof. The values “a” and “b”may be measured by a scanning electron microscope (SEM) and an opticalmicroscope. Specifically, “b” (average diameter) is obtained bymeasuring diameters of any selected 100 silver nanowires respectivelyusing the Field Emission Scanning Electron Microscope JSM-7000F(manufactured by JEOL Ltd.), and calculating the arithmetic averagethereof. Further, “a” (average length) is obtained by measuring lengthsof any selected 100 silver nanowires respectively using the ShapeMeasurement Laser Microscope VK-X200 (manufactured by KeyenceCorporation), and calculating the arithmetic average thereof.

The kind of the metal as a material for the metal nanowires may be oneselected from the group consisting of gold, silver, platinum, copper,nickel, iron, cobalt, zinc, ruthenium, rhodium, palladium, cadmium,osmium, and iridium, or may be an alloy etc., formed by combining someof these. In order to obtain a coating film having a low surfaceresistance and a high total light transmittance, containing at least oneof gold, silver, and copper is preferable. These metals have a highconductivity, and thus, when a certain surface resistance should beobtained, the density of the metal within the surface may be reduced,and high total light transmittance can be achieved. Among these metals,containing at least gold or silver is more preferable. The mostappropriate example may be the silver nanowire.

The conducting layer includes the metal nanowires and a binder resin. Asfor the binder resin, any transparent binder can be used with nolimitation. In case that metal nanowire produced by the poly-ol methodis used as a conductive material, a binder resin soluble in alcohol orwater is preferable, in view of the compatibility to the solvent forproduction (polyol). In the present specification, the expression“soluble in alcohol or water” refers to the fact that 0.1 g or morebinder resin can be solved in 1 L of alcohol or water. Specifically, thebinder may be poly-N-vinyl pyrrolidone, a water-soluble cellulose resinsuch as methyl cellulose, hydroxyethyl cellulose, carboxymethylcellulose, and the like, a butyral resin, or poly-N-vinylacetamide (PNVA(registered trademark)). The above resin may be used solely, or two ormore kinds of the resin may be used in combination. When two or morekinds of the resin are used, they may be simply mixed, or may becopolymerized.

Poly-N-vinylacetamide is a homopolymer of N-vinylacetamide (NVA), but acopolymer having 70 mol % or more of N-vinylacetamide (NVA) may also beused. Examples of a monomer which can be copolymerized with NVA include:N-vinylformamide, N-vinylpyrrolidone, acrylic acid, methacrylic acid,sodium acrylate, sodium methacrylate, acrylamide, acrylonitrile, and thelike. The more the content of the copolymerized component, the higherthe sheet resistance of the transparent conductive pattern to beobtained, the lower the adhesion between the silver nanowires and thesubstrate, and the lower the heat resistance (thermal decompositionstarting temperature). Therefore, the polymer contains the monomer unitderived from N-vinylacetamide preferably 70 mol % or more, morepreferably 80 mol % or more, and still more preferably 90 mol % or more.The polymer (homopolymer or copolymer) including N-vinylacetamide as amonomer unit has a weight average molecular weight in terms of absolutemolecular weight of preferably 30,000 to 4,000,000, more preferably100,000 to 3,000,000, and still more preferably 300,000 to 1,500,000.The absolute molecular weight is measured by the following method.

<Molecular Weight Measurement>

The binder resin was dissolved in the following eluent, which was leftto stand still for 20 hours. The concentration of the binder resin inthe resultant solution was 0.05% by mass.

The solution was filtered by a 0.45 μm membrane filter, the filtrate wasmeasured by GPC-MALS, and a weight-average molecular weight based on theabsolute molecular weight was calculated.

GPC: Shodex (registered trademark) SYSTEM 21, manufactured by ShowaDenko K.K.

Column: TSK gel (registered trademark) G6000PW, manufactured by TosohCorporation

Column Temperature: 40° C.

Eluent: 0.1 mol/L of NaH₂PO₄ aqueous solution+0.1 mol/L of Na₂HPO₄aqueous solution

Flow Rate: 0.64 mL/min

Sample Injection Volume: 100 μL

MALS Detector: DAWN (registered trademark) DSP, manufactured by WyattTechnology Corporation

Laser Wavelength: 633 nm

Multi-Angle Fitting Method: Berry Method

The conducting layer is formed by printing, as a coating liquid, aconductive ink (metal nanowire ink) containing the metal nanowires, thebinder resin, and the solvent on at least one main face of thetransparent substrate, and drying and removing the solvent.

The solvent is not particularly limited as far as the solvent has asuperior metal nanowire dispersibility, and the binder resin can bedissolved in the solvent. However, when the metal nanowire synthesizedby the poly-ol method is used as the conductive material, alcohol, wateror a mixture solvent of alcohol and water is preferable, in view of thecompatibility to the solvent used for production (polyol). As mentionedabove, a preferable binder resin is also a binder resin soluble toalcohol, water, or a mixture solvent of alcohol and water. The mixturesolvent of alcohol and water is more preferable because the drying speedof the binder resin can be easily controlled. The alcohol contains atleast one kind of saturated monohydric alcohols having 1 to 3 carbonatoms (methanol, ethanol, n-propanol, and isopropanol), which arerepresented by C_(n)H_(2n+1)OH (n being an integer of 1 to 3)(hereinbelow, simply referred to as saturated monohydric alcohol having1 to 3 carbon atoms). Containing 40% by mass or more of the saturatedmonohydric alcohol having 1 to 3 carbon atoms in the alcohol in total ispreferable. Using the saturated monohydric alcohol having 1 to 3 carbonatoms is advantageous because drying process becomes easy.

Alcohols other than the saturated monohydric alcohol having 1 to 3carbon atoms, represented by C_(n)H_(2n+1)OH (n being an integer of 1 to3) can be used together. Examples of other alcohols which can be usedtogether with the saturated monohydric alcohol having 1 to 3 carbonatoms, represented by C_(n)H_(2n+1)OH (n being an integer of 1 to 3),include ethylene glycol, propylene glycol, ethylene glycolmonomethylether, ethylene glycol monoethylether, propylene glycolmonomethylether, propylene glycol monoethylether, and the like. Usingsuch alcohol together with above-mentioned saturated monohydric alcoholhaving 1 to 3 carbon atoms represented by C_(n)H_(2n+1)OH (n being aninteger of 1 to 3) is advantageous because the drying speed can beadjusted. Further, the content of the alcohol in total in the mixturesolvent is preferably 5% to 90% by mass. when the content is less than5% by mass, or more than 90% by mass, there are drawbacks that a stripepattern (uneven coating) is generated at the time of coating.

The conductive ink can be produced by stirring and mixing the binderresin, the metal nanowires, and the solvent, using a planetarycentrifugal stirrer, and the like. The content of the binder resin inthe conductive ink is preferably in the range of 0.01% to 1.0% by mass.The content of the metal nanowire in the conductive ink is preferably inthe range of 0.01% to 1.0% by mass. The content of the solvent in theconductive ink is preferably in the range of 98.0% to 99.98% by mass. Bythe above composite, a conductive ink having a viscosity of 1 to 50mPa·s can be obtained. By printing the ink on the main face of thetransparent substrate, and drying/removing the solvent, a conductinglayer having a film thickness of 20 to 200 nm can be obtained. Theviscosity of the conductive ink is more preferably 1 to 20 mPa·s, andstill more preferably 1 to 10 mPa·s. The viscosity was measured by thedigital viscometer DV-E (spindle: SC4-18) manufactured by Brookfield, at25° C.

A method for producing the transparent conducting film (method forprinting the conductive ink) may be a bar-coating method, a gravureprinting method, an ink-jet method, a slit-coating method, and the like.Among them, the bar-coating method has a preferable coating ability of alow-viscosity ink, and a superior property for forming a thin film.Further, unlike the ink-jet method, the bar-coating method can print alow-viscosity ink containing inorganic or metal particles, withoutcausing clogging.

A method for producing a transparent conducting film according to thepresent aspect has steps of coating the above-mentioned conductive inkon at least one face (one main face) of the transparent substrate by abar-coating method, and drying the same. The coating is preferablyperformed within a range of 20 to 30° C. under an air atmosphere. Thedrying performed after the coating is preferably performed within arange of 60 to 100° C., under an air atmosphere, for 1 to 10 minutes. Inthe above bar-coat printing method, the bar coater is not particularlylimited, and can be appropriately selected in accordance with theobject. The bar used for a bar coater includes a Meyer bar (or wire bar)having a wire wounded therearound, or a wireless bar having no wire buthaving a groove formed on the bar by shaving. Because of the reasonsmentioned below, the wireless bar is preferable. The velocity V (mm/sec)that the conductive ink is coated on at least one face (one main face)of the transparent substrate by the bar-coating method (hereinafter,referred to as “coating velocity”) is a relative moving velocity of thebar relative to the transparent substrate. That is, a moving velocity ofthe bar relative to the transparent substrate during the coating, or atransferring velocity of the transparent substrate relative to the bar.Preferably, V (mm/sec) satisfies 2000≥V≥50. Satisfying V≥50 ispreferable in order to produce a transparent conducting film having asmall in-plane resistance anisotropy of the conducting layer, at a highproductivity. Also, satisfying 2000≥V can result in forming a conductinglayer having a small in-plane resistance anisotropy without causinguneven coating (blurring, etc.). The upper limit value of V(mm/sec) ismore preferably 1000, still more preferably 700, and particularlypreferably 500. Further, the lower limit value of V is more preferably100, and still more preferably 350. As shown in the below-mentionedExamples, the smaller the numerical value of the friction coefficient ofa material constituting the bar surface, the smaller the lower limitvalue of V (mm/sec) at which a conducting layer having a small in-planeresistance anisotropy can be formed without coating unevenness(blurring, etc.). Namely, when the friction coefficient of a materialconstituting the bar surface is within a range of 0.05 to 0.40, V(mm/sec) is preferably 2000≥V≥50, and more preferably 1000≥V≥100, andstill more preferably 500≥V≥100. Whereas, if the friction coefficient ismore than 0.40 and 0.70 or less, V (mm/sec) is preferably 2000≥V≥350,more preferably 1000≥V≥350, still more preferably 700≥V≥350, andparticularly preferably 500≥V≥350.

FIG. 1A, FIG. 1B, and FIG. 1C show schematic views explaining the shapeof a groove formed on a bar used in a bar coater. FIG. 1A shows anexample of a wireless bar, and FIG. 1B shows an example of Meyer bar (ora wire bar). FIG. 1C shows an example of a groove shape of a marketedwireless bar.

In FIG. 1A and FIG. 1B, P is a pitch of a groove, H is a depth of agroove, and A is a cross-sectional area of a pocket formed by thegroove. In the wireless bar shown in FIG. 1A, the groove is formed bycutting, and thus P and H can be adjusted as desired. On the other hand,the Meyer bar shown in FIG. 1B is produced by winding a wire with adiameter D around a bar, and thus, P should be D, and H should be D/2.

As shown in the below-mentioned Examples, when the groove of the bar hasa pitch (P) and a depth (H) satisfying a ratio (P/H) of 5 to 30, thein-plane resistance anisotropy of the conducting layer can be decreased,compared to the case that Meyer bar is used. In a wireless bar, P and Hcan be set as desired. If the coating is performed using a bar which hasa P/H value of 9 to 30, and has a below-mentioned friction coefficientof a material constituting the bar surface of 0.05 to 0.40, at a coatingvelocity V (mm/sec) of 2000≥V≥50; or using a bar which has a P/H valueof 9 to 30, and has a below-mentioned friction coefficient of a materialconstituting the bar surface of 0.05 to 0.45, at a coating velocityV(mm/sec) of 2000≥V≥350; (R_(TD))/(R_(MD)), which is, as mentionedbelow, an index for the in-plane resistance anisotropy of the conductinglayer, can be made 1.3 or less, which is preferable. The value of P/H ismore preferably 9.2 to 25, still more preferably 9.5 to 20, andparticularly preferably 10 to 15.

The groove of the wireless bar can have a various shape as far as thepitch (P) and the depth (H) satisfy the ratio (P/H) of 5 to 30. Forexample, as shown in FIG. 1C, the groove may have a S-shape (smoothcurved shape), a K-shape (with a slightly flat bottom), and a W-shape(with a slightly flat top and a slightly flat bottom), and all of theseshapes can be found in marketed products.

The in-plane resistance anisotropy (R_(TD))/(R_(MD)) of the conductinglayer formed on the transparent substrate by the bar-coat printingmethod is preferably 0.7 to 1.3, more preferably 0.8 to 1.2, and stillmore preferably 0.9 to 1.1. Here, (R_(MD)) refers to a resistance valueof the conducting layer in the coating direction (printing direction) ofthe conductive ink, and (R_(TD)) refers to a resistance value of theconducting layer in the direction perpendicular to the coating direction(printing direction) of the conductive ink.

The inventor of the present disclosure found out that a material formingthe wireless bar surface which contacts the transparent substrate has aninfluence on the anisotropy of the resistance value within a plane ofthe conducting layer formed by bar-coat printing. Namely, the inventorof the present disclosure found out that by using a wireless bar havinga surface constituted by a material having a friction coefficient of0.05 to 0.40, obtained by the below-mentioned measurement method, forbar-coat printing, a conducting layer having a smaller anisotropy ofresistance value (in-plane resistance anisotropy) can be obtained. It isassumed that the use of a wireless bar having the above frictioncoefficient range induces the phenomenon that the conductive inkfavorably flows not only in the printing direction (longitudinaldirection) but also in the direction perpendicular to the printingdirection (lateral direction). The friction coefficient is morepreferably 0.05 to 0.30, and still more preferably 0.05 to 0.20. Awireless bar made of a material having the above friction coefficientcan be used. However, a wireless bar having a surface made of agenerally used material (SUS, etc.) can be subjected to various surfacetreatments to adjust the friction coefficient to the above range.Examples of such treatments include: hard chrome plating with a frictioncoefficient of 0.7, electroless nickel plating with a frictioncoefficient of 0.3, electroless nickel-PTFE plating with a frictioncoefficient of 0.25, and Diamond-Like Carbon treatment with a frictionof 0.15. Note that SUS304 without any surface treatments has a frictioncoefficient of 0.45. All of the friction coefficients are catalogvalues, and the surface-treated wireless bars are commerciallyavailable.

The friction coefficient is measured by a ball-on-disk tribometer inaccordance with JIS R1613. The material of the ball is SUS304, and asubstrate made of a material same as the material of the wireless bar ora substrate surface-treated by a material same as the material of thewireless bar is used as a disk. A friction coefficient is calculated bymeasuring a frictional force generated by disk rotation by a sensor, anddividing the measured value by an applied load.

By a bar-coat printing method using a wireless bar having a groove ofthe above-mentioned specific shape, a conducting layer having a smallerin-plane resistance anisotropy, that is, preferably (R_(TD))/(R_(MD)) of0.7 to 1.3, can be formed on the transparent substrate, compared to thecase using a Meyer bar (wire bar). The value of (R_(TD))/(R_(MD)) ismore preferably 0.8 to 1.2, and still more preferably 0.9 to 1.1.

<Protection Film>

Preferably, a protection film which protects the conducting layer of thetransparent conducting film, is provided on the surface of theconducting layer. The protection film is preferably a cured film of acurable resin composite. The curable resin composite preferablycomprises (A) a polyurethane containing a carboxy group, (B) an epoxycompound, (C) a curing accelerator, and (D) a solvent. The curable resincomposite is applied on the conducting layer by printing, coating, etc.,and cured to form the protection film. Curing of the curable resincomposite can be performed by heating and drying a thermo-setting resincomposite.

The (A) polyurethane containing a carboxy group has a weight-averagemolecular weight of preferably 1,000 to 100,000, more preferably 2,000to 70,000, and still more preferably 3,000 to 50,000. The molecularweight is a polystyrene equivalent value measured by gel permeationchromatography (hereinafter, referred to as GPC). If the molecularweight is less than 1,000, the elongation property, the flexibility, andthe strength of the printed coating film may be deteriorated. Whereas,if the molecular weight exceeds 100,000, solubility of polyurethane tothe solvent decreases, and further, even if polyurethane can dissolve inthe solvent, the viscosity becomes too high, resulting in increasingrestrictions on use.

In the present specification, unless specifically described, measurementconditions of GPC are as follows.

Device Name: HPLC unit HSS-2000, manufactured by JASCO Corporation

Column: Shodex Colum LF-804

Mobile Phase: tetrahydrofuran

Flow Rate: 1.0 mL/min

Detector: RI-2031 Plus, manufactured by JASCO Corporation

Temperature: 40.0° C.

Sample Volume: sample loop 100 μL

Sample Concentration: Prepared to approximately 0.1% by mass

The (A) polyurethane containing a carboxy group has an acid value ofpreferably 10 to 140 mg-KOH/g, and more preferably 15 to 130 mg-KOH/g.If the acid value is 10 mg-KOH/g or more, both the curing property andthe solvent resistance are superior. If the acid value 140 mg-KOH/g orless, the solubility to the solvent as a urethane resin is superior, andadjustment to a desirable viscosity is easy. In addition, problems suchthat the cured product becomes too hard and warpage, etc., of thesubstrate film occurs, can be prevented.

Further, in the present specification, the acid value of a resin is avalue measured by the following method.

Approximately 0.2 g of sample is precisely weighed by a precisionbalance into a 100 ml Erlenmeyer flask, and 10 ml of a mixture solventof ethanol/toluene=1/2 (mass ratio) is provided thereto to dissolve thesample. Further, 1 to 3 drops of a phenolphthalein ethanol solution isadded to the container as an indicator, which is sufficiently stirreduntil the sample becomes uniform. The resultant is subjected totitration with a 0.1 N potassium hydroxide-ethanol solution. When theindicator continues to be in light red for 30 seconds, it is determinedthat the neutralization ends. The value obtained from the result usingthe following calculation formula is treated as an acid value of theresin.

Acid Value (mg-KOH/g)=[B×f×5.611]/S

B: Use amount (ml) of 0.1 N potassium hydroxide-ethanol solution

f: Factor of 0.1 N potassium hydroxide-ethanol solution

S: Collection quantity (g) of sample

More specifically, the (A) polyurethane containing a carboxy group ispolyurethane synthesized by using (a1) a polyisocyanate compound, (a2) apolyol compound, and (a3) a dihydroxy compound containing a carboxygroup, as monomers. From the viewpoints of weather resistance and lightresistance, preferably, each of (a1), (a2), and (a3) does not contain afunctional group with conjugate properties such as an aromatic compound.Hereinbelow, each monomer will be explained in more detail.

(a1) Polyisocyanate Compound

For (a1) polyisocyanate compound, usually, diisocyanate which has twoisocyanato groups per molecule is used. Examples of the polyisocyanatecompound include: aliphatic polyisocyanate, alicyclic polyisocyanate,and the like. One of them may be used by itself, or two or more of themmay be used in combination. As far as (A) polyurethane containing acarboxy group is not turned into a gel, a small amount of polyisocyanatehaving three or more isocyanato groups may also be used.

Examples of the aliphatic polyisocyanate include: 1,3-trimethylenediisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylenediisocyanate, 1,9-nonamethylene diisocyanate, 1,10-decamethylenediisocyanate, 2,2,4-trimethylhexamethylene diisocyanate,2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate,2,2′-diethyl ether diisocyanate, dimer acid diisocyanate, and the like.

Examples of the alicyclic polyisocyanate include: 1,4-cyclohexanediisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane,1,4-bis(isocyanatomethyl)cyclohexane,3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI,isophorone diisocyanate), bis-(4-isocyanatocyclohexyl)methane(Hydrogenated MDI), hydrogenated (1,3- or 1,4-)xylylene diisocyanate,norbornane diisocyanate, and the like.

Here, if an alicyclic compound having 6 to 30 carbon atoms other thanthe carbon atoms in the isocyanato group (—NCO group) is used as (a1)polyisocyanate compound, a protection film formed by the polyurethaneresin according to the present aspect has high reliability particularlyunder high temperature and high humidity, and is suitable as a memberfor an electronic device component. Among the above examples of thealicyclic polyisocyanate, 1,4-cyclohexane diisocyanate, isophoronediisocyanate, bis-(4-isocyanatocyclohexyl)methane,1,3-bis(isocyanatomethyl)cyclohexane, and1,4-bis(isocyanatomethyl)cyclohexane, are preferable.

From the viewpoints of weather resistance and light resistance, as for(a1) polyisocyanate compound, using a compound which does not have anaromatic ring is preferable. Thus, when the aromatic polyisocyanate orthe aromatic-aliphatic polyisocyanate used in accordance with needs, thecontent thereof is preferably 50 mol % or less, more preferably 30 mol %or less, and still more preferably 10 mol % or less, relative to thetotal amount (100 mol %) of (a1) polyisocyanate compound.

(a2) Polyol Compound

The number average molecular weight of (a2) polyol compound (with theproviso that (a2) polyol compound does not include (a3) dihydroxycompound having a carboxy group) is usually 250 to 50,000, preferably400 to 10,000, and more preferably 500 to 5,000. The molecular weight isa polystyrene equivalent value measured by the GPC under the abovementioned conditions.

Preferably, (a2) polyol compound is diol having hydroxy groups at bothends. Examples of (a2) polyol compound include: polycarbonate polyol,polyether polyol, polyester polyol, polylactone polyol, polysiliconehaving hydroxy groups at both ends, and a polyol compound having 18 to72 carbon atoms obtained by adding hydrogen to a C18 (carbon atom number18) unsaturated fatty acid made from vegetable oil and a polycarboxilicacid derived from a polymer of the C18 unsaturated fatty acid, andconverting the carboxylic acid into hydroxy groups. Among them, in viewof the balance of the water resistance, the insulation reliability, andthe adhesion to a substrate as a protection film, polycarbonate polyolis preferable.

The polycarbonate polyol can be obtained from diol having 3 to 18 carbonatoms as a raw material, through reaction with carbonate ester orphosgene, and can be represented by, for example, the followingstructural formula (1):

In Formula (1), R³ represents a residue obtained by removing a hydroxygroup from a corresponding diol (HO—R³—OH), which is an alkylene grouphaving 3 to 18 carbon atoms, n₃ represents a positive integer, which ispreferably 2 to 50.

Specific examples of the raw material used for producing thepolycarbonate polyol represented by Formula (1) include:1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol,3-methyl-1,5-pentanediol, 1,8-octanediol, 1,3-cyclohexanedimethanol,1,4-cyclohexanedimethanol, 1,9-nonanediol, 2-methyl-1,8-octanediol,1,10-decamethylene glycol, and 1,2-tetradecanediol, etc.

The polycarbonate polyol may be a polycarbonate polyol (copolymerizedpolycarbonate polyol) having a plurality of types of alkylene groups inits skeleton. Using a copolymerized polycarbonate polyol is advantageousin many cases from the viewpoint of preventing crystallization of (A)polyurethane containing a carboxyl group. Further, taking the solubilityto the solvent into account, using, in combination, a polycarbonatepolyol having a branched skeleton and having hydroxy groups at the endsof the branched chains, is preferable.

(a3) Dihydroxy Compound Containing Carboxy Group

Preferably, (a3) a dihydroxy compound containing a carboxy group is acarboxylic acid or an amino carboxylic acid having a molecular weight of200 or less, having two groups selected from a hydroxy group, ahydroxyalkyl group with one carbon, and a hydroxyalkyl group with 2carbons, because a cross linking point is controllable. Specificexamples include: 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoicacid, N,N-bis hydroxyethyl glycine, N,N-bis hydroxyethyl alanine, andthe like. Among them, in view of the solubility to the solvent,2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid areparticularly preferable. One type of the compounds of (a3) dihydroxycompound containing a carboxy group can be used by itself, or two ormore types may be used in combination.

The above-mentioned (A) a polyurethane containing a carboxy group can besynthesized from the above three components ((a1), (a2), and (a3)) only.However, (a4) a monohydroxy compound and/or (a5) a monoisocyanatecompound may be further reacted for synthesis. In view of the lightresistance, using a compound which does not have an aromatic ring and acarbon-carbon double bond in a molecule is preferable.

The above-mentioned (A) polyurethane containing a carboxy group can besynthesized by reacting the above-mentioned (a1) polyisocyanatecompound, (a2) polyol compound, and (a3) dihydroxy compound containing acarboxy group, under the presence or absence of a known urethanizationcatalyst such as dibutyltin dilaurate, using an appropriate organicsolvent. However, performing reaction without a catalyst is preferablebecause there would be no need to concern about the mixing of tin, etc.,in the final product.

The organic solvent is not particularly limited as far as the reactivitywith the isocyanate compound is low, but a preferable solvent is asolvent free from a basic functional group such as amine, etc., andhaving a boiling point of 50° C. or higher, preferably 80° C. or higher,and more preferably 100° C. or higher. Examples of such a solventinclude: toluene, xylylene, ethylbenzene, nitrobenzene, cyclohexane,isophorone, diethylene glycol dimethyl ether, ethylene glycol diethylether, ethylene glycol monomethyl ether acetate, propylene glycolmonomethyl ether acetate, propylene glycol monoethyl ether acetate,dipropylene glycol monomethyl ether acetate, diethylene glycol monoethylether acetate, methyl methoxypropionate, ethyl methoxypropionate, methylethoxypropionate, ethyl ethoxypropionate, ethyl acetate, n-butylacetate, isoamyl acetate, ethyl lactate, acetone, methyl ethyl ketone,cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide,N-methylpyrrolidone, γ-butyrolactone, dimethyl sulfoxide, and the like.

Taking into account that it is not preferable to use an organic solventin which the polyurethane to be generated does not dissolve well, andthat the polyurethane is used as a raw material of an ink for theprotection film, in the usage as an electronic material, propyleneglycol monomethyl ether acetate, propylene glycol monoethyl etheracetate, dipropylene glycol monomethyl ether acetate, diethylene glycolmonoethyl ether acetate, γ-butyrolactone, etc., are particularlypreferable among the above.

The addition sequence of the raw materials is not limited, but usually,first, (a2) polyol compound and (a3) dihydroxy compound having a carboxygroup are provided, and dissolved or dispersed in the solvent, andthereafter, (a1) polyisocyanate compound is added by dropping at 20 to150° C., and more preferably at 60 to 120° C., which is then reacted at30 to 160° C., and preferably at 50 to 130° C.

The molar ratio of the added raw materials is adjusted in accordancewith the molecular weight and the acid value of the objectedpolyurethane.

Specifically, the molar ratio of the provided materials is thatisocyanato group of (a1) polyisocyanate compound: (hydroxy group of (a2)polyol compound+hydroxy group of (a3) dihydroxy compound having acarboxy group) is 0.5 to 1.5:1, preferably 0.8 to 1.2:1, and morepreferably 0.95 to 1.05:1.

Further, hydroxy group of (a2) polyol compound: hydroxy group (a3)dihydroxy compound having a carboxy group is 1:0.1 to 30, and preferably1:0.3 to 10.

Examples of (B) epoxy compound include: an epoxy compound having two ormore epoxy groups in one molecule, such as bisphenol-A type epoxy resin,hydrogenated bisphenol-A type epoxy resin, bisphenol-F type epoxy resin,novolak type epoxy resin, phenol novolak type epoxy resin, cresolnovolak type epoxy resin, N-glycidyl type epoxy resin, bisphenol Anovolak type epoxy resin, chelate type epoxy resin, glyoxal type epoxyresin, amino group-containing epoxy resin, rubber-modified epoxy resin,dicyclopentadiene phenolic type epoxy resin, silicone-modified epoxyresin, ε-caprolactone-modified epoxy resin, aliphatic-type epoxy resincontaining a glycidyl group, alicyclic epoxy resin containing a glycidylgroup, etc.

In particular, an epoxy compound having three or more epoxy groups inone molecule is more preferable. Examples of such an epoxy compoundinclude: EHPE (registered trademark) 3150 (manufactured by DaicelCorporation), jER (registered trademark) 604 (manufactured by MitsubishiChemical Corporation), EPICLON (registered trademark) EXA-4700(manufactured by DIC Corporation), EPICLON (registered trademark)HP-7200 (manufactured by DIC Corporation), pentaerythritol tetraglycidylether, pentaerythritol triglycidyl ether, TEPIC (registered trademark)-S(manufactured by Nissan Chemical Corporation), and the like.

The (B) epoxy compound may contain an aromatic ring in a molecule, andin this case, the mass of (B) is preferably 20% by mass or less,relative to the total mass of (A) and (B).

The mixing ratio of (A) polyurethane containing a carboxy group relativeto (B) epoxy compound is preferably 0.5 to 1.5, more preferably 0.7 to1.3, and still more preferably 0.9 to 1.1, in terms of equivalent ratioof the carboxy groups of polyurethane relative to the epoxy groups of(B) epoxy compound.

Examples of (C) curing accelerator include: a phosphine-based compoundsuch as triphenylphosphine, tributylphosphine (manufactured by HokkoChemical Industry Co., Ltd.), Curezol (registered trademark)(imidazole-based epoxy resin curing agent: manufactured by ShikokuChemicals Corporation), 2-phenyl-4-methyl-5-hydroxy methyl imidazole,U-CAT (registered trademark) SA series (DBU salt: manufactured bySan-Apro Ltd.), Irgacure (registered trademark) 184, and the like. Withrespect to the used amount of these, if the amount is too small, theeffect of addition cannot be obtained, whereas if the amount is toolarge, the electric insulation is decreased. Therefore, 0.1 to 10% bymass, more preferably 0.5 to 6% by mass, still more preferably 0.5 to 5%by mass, and particularly preferably 0.5 to 3% by mass, is used,relative to the total mass of (A) and (B).

Further, a curing aid may be used together. The curing aid may be apolyfunctional thiol compound, an oxetane compound, and the like.Examples of the polyfunctional thiol compound include: pentaerythritoltetrakis(3-mercaptopropionate),tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, trimethylolpropanetris(3-mercaptopropionate), Karenz (registered trademark) MT series(manufactured by Showa Denko K.K.), and the like. Examples of theoxetane compound include: ARON OXETANE (registered trademark) series(manufactured by Toagosei Co., Ltd.), ETERNACOLL (registered trademark)OXBP or OXMA (manufactured by Ube Industries Ltd.), and the like. Withrespect to the used amount, if the amount is too small, the effect ofaddition cannot be obtained, whereas if the amount is too large, thecuring rate becomes too high, resulting in decreasing handling property.Therefore, 0.1 to 10% by mass, and preferably 0.5 to 6% by mass is used,relative to the mass of (B).

The content of (D) solvent used in the curable resin composite ispreferably 95.0% by mass or more and 99.9% by mass or less, morepreferably 96% by mass or more and 99.7% by mass or less, and still morepreferably 97% by mass or more and 99.5% by mass or less. (D) solventcan be the solvent used for synthesizing (A) polyurethane containing acarboxy group as it is. Further, other solvent may be used for (D) inorder to adjust the solubility of polyurethane or printability. Whenother solvent is used, the reaction solvent may be distilled away beforeor after a new solvent is added, to replace the solvent. Taking intoaccount the cumbersomeness of operations and the energy cost, using atleast a part of the solvent used for synthesizing (A) polyurethanecontaining a carboxy group as it is, is preferable. Taking into accountthe stability of the composite for the protection film, the solvent hasa boiling point of preferably 80° C. to 300° C., and more preferably 80°C. to 250° C. If the boiling point is lower than 80° C., drying easilyproceeds during the printing, which causes unevenness. If the boilingpoint is higher than 300° C., heat treatment at a high temperature for along time is required for drying and curing, which is not suitable forindustrial production.

Examples of the solvent include: a solvent used for synthesizingpolyurethane such as propylene glycol monomethyl ether acetate (boilingpoint 146° C.), γ-butyrolactone (boiling point 204° C.), diethyleneglycol monoethyl ether acetate (boiling point 218° C.), tripropyleneglycol dimethyl ether (boiling point 243° C.), etc., an ether-basedsolvent such as propylene glycol dimethyl ether (boiling point 97° C.),diethylene glycol dimethyl ether (boiling point 162° C.), etc., asolvent having a hydroxy group such as isopropyl alcohol (boiling point82° C.), t-butyl alcohol (boiling point 82° C.), 1-hexanol (boilingpoint 157° C.), propylene glycol monomethyl ether (boiling point 120°C.), diethylene glycol monomethyl ether (boiling point 194° C.),diethylene glycol monoethyl ether (boiling point 196° C.), diethyleneglycol monobutyl ether (boiling point 230° C.), triethylene glycol(boiling point 276° C.), ethyl lactate (boiling point 154° C.), etc.,and methyl ethyl ketone (boiling point 80° C.), and ethyl acetate(boiling point 77° C.). One of these solvents may be used by itself, ora mixture of two or more types of them may be used. When two or moretypes of solvents are mixed, using a solvent having a hydroxy group andhaving a boiling point exceeding 100° C. in view of the solubility ofthe used polyurethane resin, epoxy resin, etc., and in order to preventaggregation or precipitation, or using a solvent having a boiling pointof 100° C. or lower in view of the drying property of the ink, inaddition to the solvent used for synthesizing (A) polyurethanecontaining a carboxy group, is preferable.

The above mentioned curable resin composite can be produced by mixing(A) polyurethane containing a carboxy group, (B) epoxy compound, (C)curing accelerator, and (D) solvent so that the content of (D) solventbecomes 95.0% by mass or more and 99.9% by mass or less, and stirringthe mixture until the mixture becomes uniform.

The solid content in the curable resin composite may differ depending onthe desired film thickness or printing method, but is preferably 0.1 to10% by mass, and more preferably 0.5% by mass to 5% by mass by mass. Ifthe solid content is within the range of 0.1 to 10% by mass, when thecomposite is coated on a conducting film, drawbacks such that theelectrical contact from silver paste, etc., cannot be obtained due tothe too large thickness, do not occur, and a protection film having asufficient weather resistance and light resistance and a thickness of 50to 500 nm can be obtained.

From the viewpoint of light resistance, the content of an aromaticring-containing compound defined by the formula below is restricted topreferably 15% by mass or less, in the protection film (the solidcontent in the protection film ink, i.e., (A) polyurethane containing acarboxy group, (B) epoxy compound, and curing residue of (C) curingaccelerator). Here, considering that all or a part of (C) curingaccelerator may disappear (by decomposition, volatilization, etc.)depending on curing conditions, “curing residue of (C) curingaccelerator” refers to the (C) curing accelerator which remains in theprotection film under the curing conditions. Further, “aromaticring-containing compound” refers to a compound having at least onearomatic ring in molecule.[(use amount of aromatic ring-containing compound)/(mass of protectionfilm (mass of (A) polyurethane containing a carboxyl group+mass of (B)epoxy compound+curing residue of (C) curing accelerator))]*100(%)

The above mentioned curable resin composite is used for forming aprotection film, by coating the curable resin composite on thetransparent substrate (transparent conducting film) having thereon aconducting layer containing metal nanowires using a printing method suchas a bar-coating printing, gravure printing, inkjet printing, slitcoating, and the like, drying and removing the solvent, and curing thecurable resin.

EXAMPLE

Hereinbelow, specific examples of the present disclosure will bespecifically explained. The examples are described below for the purposeof easy understanding of the present disclosure, and the presentdisclosure is not limited to these examples.

<Outline of Transparent Conducting film Evaluation Method>

A conductive ink containing a silver nanowire, a binder resin, and asolvent was produced, and thereafter, the ink was coated on one mainface of the transparent substrate using a bar coater, and dried to forma conducting layer. Subsequently, a protection film ink was produced,which was coated on the conducting layer and dried to form a protectionfilm. Thereby, a transparent conducting film was produced. At this time,the coating direction of the conductive ink on the transparent substratesurface was defined as MD, and the direction perpendicular to thecoating direction was defined as TD. A test piece was produced, and aresistance value between two points was measured as mentioned below, tostudy the in-plane resistance anisotropy of the conducting layer.

Example 1

<Preparation of Silver Nanowire>

Polyvinylpyrrolidone K-90 (manufactured by Nippon Shokubai Co., Ltd.)(0.98 g), AgNO₃ (1.04 g), and FeCl₃ (0.8 mg) were dissolved in ethyleneglycol (250 ml), and subjected to thermal reaction at 150° C. for onehour. The obtained silver nanowire coarse dispersion liquid wasdispersed in 2000 ml of methanol, which was poured into a desktop smalltester (using ceramic membrane filter Cefilt, membrane area: 0.24 m²,pore size: 2.0 μm, size Φ: 30 mm×250 mm, filter differential pressure:0.01 MPa, manufactured by NGK Insulators, Ltd.), and was subjected tocross-flow filtration at a circulation flow rate of 12 L/min and adispersion liquid temperature of 25° C., to remove impurities, and tothereby obtain silver nanowires (average diameter: 26 nm, averagelength: 20 μm). The average diameter of the obtained silver nanowireswas obtained by measuring diameters of arbitrarily selected 100 silvernanowires using Field Emission Scanning Electron Microscope JSM-7000F(manufactured by JEOL Ltd.), and calculating the arithmetic averagevalue of the measurement results. Further, the average length of theobtained silver nanowires was obtained by measuring lengths ofarbitrarily selected 100 silver nanowires using the Shape MeasurementLaser Microscope VK-X200 (manufactured by Keyence Corporation), andcalculating the arithmetic average value of the measurement results. Forthe methanol, ethylene glycol, AgNO₃, and FeCl₃, those manufactured byFUJIFILM Wako Pure Chemical Corporation were used.

<Preparation of Conductive Ink (Silver Nanowire Ink)>

11 g of dispersion liquid having a water/methanol/ethanol mixturesolvent and silver nanowires synthesized by the above polyol method(silver nanowire concentration: 0.62% by mass,water/methanol/ethanol=10:20:70[mass ratio]), 2.4 g of water, 3.6 g ofmethanol (manufactured by FUJIFILM Wako Pure Chemical Corporation), 8.3g of ethanol (manufactured by FUJIFILM Wako Pure Chemical Corporation),12.8 g of propyleneglycol monomethyl ether (PGME, manufactured byFUJIFILM Wako Pure Chemical Corporation), 1.2 g of propylene glycol (PG,manufactured by AGC Inc.), and 0.7 g of PNVA (registered trademark)aqueous solution (solid content concentration: 10% by mass,weight-average molecular weight: 900,000, manufactured by Showa DenkoK.K.) were mixed and stirred by Mix Rotor VMR-5R (manufactured by AS ONECorporation) for 1 hour, at a room temperature and under an airatmosphere (rotation speed: 100 rpm), to thereby produce 40 g of silvernanowire ink.

Table 1 shows concentrations of the silver nanowires in the obtainedsilver nanowire inks and viscosities of the silver nanowire inks. Thesilver concentration of the obtained silver nanowire ink was measured byAA280Z Zeeman atomic absorption spectrophotometer, manufactured byVarian. The viscosity was measured by the digital viscometer DV-E(spindle: SC4-18) manufactured by Brookfield, at 25° C.

<Forming Conducting layer (Silver Nanowire Layer)>

As a transparent substrate, a cyclo olefin polymer (COP) film ZF14(glass transition temperature: 136° C. [catalog value], thickness: 100μm, manufactured by Zeon Corporation) of A4 size was subjected to plasmatreatment (used gas: nitrogen, feed speed: 50 mm/sec, treatment time: 6sec, set voltage: 400 V) using a plasma processing equipment (AP-T03manufactured by Sekisui Chemical Co., Ltd.). A silver nanowire ink wascoated on the entire surface of one main face of the transparentsubstrate (ZF14-013) at a room temperature and under an air atmosphere(coating speed V: 500 mm/sec), by using TQC Automatic Film ApplicatorStandard (manufactured by COTEC Corporation), and wireless barOSP-CN-22L (groove shape of bar: S-shape/pitch(P): 500 μm, depth(H): 42μm, P/H: 11.9, material: SUS304, manufactured by COTEC Corporation).Thereafter, the coated film was subjected to hot-air drying at 80° C.,for 1 minute, and under an air atmosphere, by using a constanttemperature oven HISPEC HS350 (manufactured by Kusumoto Chemicals Ltd.),and thereby a silver nanowire layer was obtained.

<Film Thickness Measurement>

The thickness of the conducting layer (silver nanowire layer) wasmeasured by a film thickness measurement system F20-UV (manufactured byFilmetrics Corporation), based on optical interferometry. Measurementwas performed at three different points, and an average value thereofwas used as a thickness. For analysis, 450 nm to 800 nm spectrum wasused. According to this measurement system, the thickness (Tc) of thesilver nanowire layer formed on the transparent substrate can bedirectly measured. The measurement results are shown in Table 1.

<Preparation of Curable Resin composite>

Synthesis Example of (A) Polyurethane Containing Carboxy Group SynthesisExample 1: Synthesis of Original Resin Used for Curable Resin CompositeOC022

42.32 g of C-1015N (polycarbonate diol, molar ratio of raw materialdiols: 1,9-nonanediol:2-methyl-1,8-octanediol=15:85, molecular weight:964, manufactured by Kuraray Co., Ltd.) as a polyol compound, 27.32 g of2,2-dimethylol butanoic acid (manufactured by Nihon Kasei Co., Ltd.) asa dihydroxy compound containing a carboxy group, and 158 g of diethyleneglycol monoethyl ether acetate (manufactured by Daicel Corporation) as asolvent were provided in a 2 L three-neck flask having a stirrer, athermometer, and a condenser, and the 2,2-dimethylol butanoic acid wasdissolved at 90° C.

The temperature of the reaction liquid was lowered to 70° C., and 59.69g of Desmodur (registered trademark)-W(bis-(4-isocyanatocyclohexyl)methane), manufactured by Sumika CovestroUrethane Co., Ltd.) as polyisocyanate was dropped thereto for 30 minutesby a dropping funnel. After the dropping was complete, the temperaturewas raised to 120° C., and the reaction was performed at 120° C. for 6hours. After the confirmation by IR that almost all of the isocyanatedisappeared, 0.5 g of isobutanol was added, which was further reacted at120° C. for 6 hours. The obtained carboxy group-containing polyurethanehad a weight average molecular weight, obtained by GPC, of 32300, and aresin solution thereof had an acid value of 35.8 mgKOH/g.

Curable Resin composite Example 1

10.0 g of above obtained (A) polyurethane containing a carboxy groupsolution (content of polyurethane containing a carboxy group: 45% bymass) was weighed in a polyethylene container, and 85.3 g of 1-hexanoland 85.2 g of ethyl acetate as (D) solvent were added thereto, which wasstirred by Mix Rotor VMR-5R (manufactured by AS ONE Corporation) for 12hours, at a room temperature and under an air atmosphere (rotationspeed: 100 rpm). When the mixture was visually confirmed as beinguniform, 0.63 g of pentaerythritol tetraglycidyl ether (manufactured byShowa Denko K.K.) as (B) epoxy compound and 0.31 g of U-CAT (registeredtrademark) 5003 (manufactured by San-Apro Ltd.) as (C) curingaccelerator, were added thereto, which were stirred again by Mix Rotorfor 1 hour. Thereby, a curable resin composite example 1 (protectionfilm ink example 1) was obtained. The ratio of the curing accelerator,i.e., an aromatic ring-containing compound in the solid content of thecurable resin composite example 1 (protection film formed by the curableresin composite example 1) was 5.7% by mass.

<Forming Protection Film>

The protection film ink example 1 was coated on the silver nanowirelayer formed on the transparent substrate (coating velocity V 500mm/sec) as below, by using TQC Automatic Film Applicator Standard(manufactured by COTEC Corporation). Coating was performed at a roomtemperature and under an air atmosphere using a wireless bar OSP-CN-05M,to have a wet film thickness of 5 μm. Thereafter, the coated film wassubjected to hot-air drying at 80° C., for 1 minute, and under an airatmosphere, by using a constant temperature oven HISPEC HS350(manufactured by Kusumoto Chemicals Ltd.), and thereby a protection film(film thickness: 80 nm) was obtained. This was a transparent conductingfilm of Example 1.

<Film Thickness Measurement>

Same as the above-mentioned film thickness measurement of the silvernanowire layer, the film thickness of the protection film was measuredby a film thickness measurement system F20-UV (manufactured byFilmetrics Corporation), based on optical interferometry. Measurementwas performed at three different points, and an average value thereofwas used as a thickness. For analysis, 450 nm to 800 nm spectrum wasused. According to this measurement system, the total thickness(T_(c+)T_(p)) can be directly measured, where the thickness (T_(c)) isthe thickness of the silver nanowire layer formed on the transparentsubstrate, and the thickness (T_(p)) is the thickness of the protectionfilm formed on the silver nanowire layer. Therefore, by subtracting thepreviously measured thickness (T_(c)) of the silver nanowire layer onlyfrom the total thickness (T_(c+)T_(p)), the thickness (T_(p)) of theprotection film can be obtained.

<Measurement of Resistance Value between Two Points>

A test piece was made by cutting a A4-size transparent conducting filminto a 20 mm*50 mm size, and forming terminals with a silver paste onthe protection film so that the distance between the terminals was 40mm. For the silver paste, the conductive paste DW-420L-2A (manufacturedby Toyobo Co., Ltd.) was used. The paste was coated by hand to be asquare of approximately 2 mm, which was subjected to hot-air drying inthe constant temperature oven HISPEC HS350 (manufactured by KusumotoChemicals Ltd.), at 80° C., for 30 minutes, under an air atmosphere.Thereby, terminal portions were made. Thereafter, the resistance valuebetween the terminals was measured. Because the protection film was thin(the silver nanowire was projected from the surface of the protectionfilm), the silver paste is conductive with the conducting layer. Inorder to electrically connect the transparent conducting pattern usingthe silver nanowires and the conductive paste pattern, a part of thesilver nanowire (the end of the wire, the intersection of wires wherewires are raised in the height direction) should be exposed from thesurface of the overcoat layer. The more the exposed portions, the easierthe electrical connection between the transparent conducting patternusing the silver nanowires and the conductive paste pattern. Thepreferable thickness of the overcoat layer may depend on the shape(diameter, length) of the silver nanowire, and the number of silvernanowires coated on the substrate, and thus, cannot be generallydetermined. However, when the thickness of the overcoat layer is small,i.e., for example 500 nm or less, preferably 200 nm or less, and morepreferably 100 nm or less, the number of exposed portions becomessufficient for obtaining the electrical connection. In the presentExample, the overcoat layer is thin with a thickness 80 nm, and thus,the silver paste is conductive with the conducting layer. When theovercoat layer is thick and obtaining the electrical connection isdifficult, the overcoat layer may be removed by a known etchingtechnology, to expose the silver nanowires.

FIG. 2A and FIG. 2B show explanatory views explaining a resistance valuemeasurement method. In FIG. 2A, the coating direction (printingdirection) is shown by the arrow. Sample S1 was cut out to have itslongitudinal direction in the coating direction. Sample S2 was cut outto have its longitudinal direction in the direction perpendicular to thecoating direction.

Next, as shown in FIG. 2B, regarding each of Sample S1 and Sample S2,the resistance value between the silver paste terminals formed by theabove-mentioned method was measured by Digital Multimeter PC5000a(manufactured by Sanwa Electric Instrument Co., Ltd.). The resistancevalue (R_(MD)) of Sample S1 coated and cut out as above, and theresistance value (R_(TD)) of Sample S2 were respectively measured, and aresistance value ratio (R_(TD))/(R_(MD)) was calculated, to therebyevaluate the in-plane resistance anisotropy.

<Sheet Resistance Measurement>

A test piece of 3 cm*3 cm was cut out from the above-mentioned A4-sizetransparent conducting film. A probe of a manual type non-contactresistance measurement instrument EC-80P (manufactured by NapsonCorporation) was placed at the center of the protection film of the testpiece, and measurement was performed. The measurement results are shownin Table 1.

<Measurement of Total Light Transmittance and Haze>

Using the above 3 cm*3 cm test piece, measurement was performed by Hazemeter NDH 2000 (manufactured by Nippon Denshoku Industries Co., Ltd.).The measurement results are shown in Table 1.

Example 2

Except that a silver nanowire ink having a silver concentration of 0.25%by mass was used, other conditions were the same as those of Example 1.The results are shown in Table 1.

Example 3

Except that a silver nanowire ink having a silver nanowire shape with anaverage diameter of 25 nm and an average length of 17 μm was used, otherconditions were the same as those of Example 1. The results are shown inTable 1.

Example 4

Except that a silver nanowire ink having a silver nanowire shape with anaverage diameter of 24 nm and an average length of 12 μm was used, otherconditions were the same as those of Example 1. The results are shown inTable 1.

Example 5

Except that a wireless bar OSP-CN-10M (manufactured by CotecCorporation, bar groove shape: S-shape, P: 200 μm, H: 21 μm, P/H: 9.5)was used, other conditions were the same as those of Example 1. Theresults are shown in Table 1.

Example 6

Except that a silver nanowire ink having a silver concentration of 0.25%by mass was used, other conditions were the same as those of Example 5.The results are shown in Table 1.

Example 7

Except that a wireless bar OSP-CN-15L (manufactured by CotecCorporation, bar groove shape: S-shape/P: 500 μm, H: 27 μm, P/H: 18.5)was used, other conditions were the same as those of Example 1. Theresults are shown in Table 1.

Example 8

Except that a wireless bar OSP-CN-18L (manufactured by CotecCorporation, bar groove shape: S-shape/P: 500 μm, H: 33 μm, P/H: 15.1)was used, other conditions were the same as those of Example 1. Theresults are shown in Table 1.

Example 9

Except that PVP (K-90, manufactured by FUJIFILM Wako Pure ChemicalCorporation), instead of PNVA, was used as a binder resin of a silvernanowire ink, other conditions were the same as those of Example 1. Theresults are shown in Table 1.

Example 10

Except that PET (untreated surface of COSMOSHINE A4100, manufactured byToyobo Co., Ltd.) was used as a transparent substrate, other conditionswere the same as those of Example 1. The results are shown in Table 1.

Example 11

Except that PC (untreated surface of FS2000H, manufactured by MitsubishiGas Chemical Company, Inc.) was used as a transparent substrate, otherconditions were the same as those of Example 1. The results are shown inTable 1.

Example 12

Except that a coating velocity V of the silver nanowire ink was 350mm/sec, other conditions were the same as those of Example 1. Theresults are shown in Table 1.

Example 13

Except that a wireless bar WP0.4H23K (bar groove shape: K-shape/P: 400μm, H: 23 μm, P/H: 17.4, manufactured by OSG System Products Co., Ltd.)was used, other conditions were the same as those of Example 1. Theresults are shown in Table 1.

Example 14

Except that a wireless bar WP0.4H38W (bar groove shape: W-shape/P: 400μm, H: 38 μm, P/H: 10.5, manufactured by OSG System Products Co., Ltd.)was used, other conditions were the same as those of Example 1. Theresults are shown in Table 1.

Example 15

Except that a wireless bar OSP-CN-22M (bar groove shape: S-shape/P: 250μm, H: 49 μm, P/H: 5.1, manufactured by Cotec Corporation) was used,other conditions were the same as those of Example 2. The results areshown in Table 1.

Example 16

Except that a wireless bar OSP-CN-17M (bar groove shape: S-shape/P: 250μm, H: 35 μm, P/H: 5.7, manufactured by Cotec Corporation) was used,other conditions were the same as those of Example 1. The results areshown in Table 1.

Example 17

Except that a coating velocity V of the silver nanowire ink was 100mm/sec, other conditions were the same as those of Example 5. Theresults are shown in Table 1.

Example 18

Except that a coating velocity V of the silver nanowire ink was 300mm/sec, other conditions were the same as those of Example 1. Theresults are shown in Table 1.

Example 19

Except that a coating velocity V of the silver nanowire ink was 100mm/sec, other conditions were the same as those of Example 4. Theresults are shown in Table 1.

Comparative Example 1

Except that a wire bar #8 (using wire of ΦD=200 μm) was used, otherconditions were the same as those of Example 2. The results are shown inTable 1.

TABLE 1 Unit Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex.10 Silver Nanowire nm 26 26 25 24 26 26 26 26 26 26 Average DiameterSilver Nanowire μm 20 20 17 12 20 20 20 20 20 20 Average Length InkSilver mass % 0.17 0.25 0.17 0.17 0.17 0.25 0.17 0.17 0.17 0.17Concentration Binder Resin Type PNVA PNVA PNVA PNVA PNVA PNVA PNVA PNVAPVP K90 PNVA Ink Viscosity mPa · s 4.1 5.2 4.0 4.0 4.1 5.2 4.1 4.1 3.54.1 (25° C.) Bar Shape Shape S S S S S S S S S S Pitch (P) μm 500 500500 500 200 200 500 500 500 500 Depth (H) μm 42 42 42 42 21 21 27 33 4242 P/H 11.9 11.9 11.9 11.9 9.5 9.5 18.5 15.1 11.9 11.9 Coating V mm/sec500 500 500 500 500 500 500 500 500 500 Velocity Silver Nanowire nm 9090 90 90 40 40 60 75 90 90 Layer Thickness Film Substrate COP COP COPCOP COP COP COP COP COP PET Resistance MD Ω 84.6 73.9 91.2 106.9 227.5201.9 177.7 120.5 101.8 82.0 Value TD Ω 89.9 81.2 100.8 105.7 231.0205.0 192.1 131.7 107.2 90.3 TD/MD 1.06 1.10 1.10 0.99 1.02 1.02 1.081.09 1.05 1.10 Sheet Resistance Ω/□ 40 31 43 37 130 100 83 54 58 36Total Light % 90 90 90 90 90 90 90 90 90 90 Transmittance Haze % 0.811.15 0.64 0.54 0.30 0.50 0.50 0.70 0.90 1.44 Ex. 11 Ex. 12 Ex. 13 Ex. 14Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex. 19 Com. Ex. 1 Silver Nanowire 26 26 2626 26 26 26 26 24 26 Average Diameter Silver Nanowire 20 20 20 20 20 2020 20 12 20 Average Length Ink Silver 0.17 0.17 0.17 0.17 0.25 0.17 0.170.17 0.17 0.25 Concentration Binder Resin PNVA PNVA PNVA PNVA PNVA PNVAPNVA PNVA PNVA PNVA Ink Viscosity 4.1 4.1 4.1 4.1 5.2 4.1 4.1 4.1 4.05.2 Bar Shape Shape S S K W S S S S S — Pitch (P) 500 500 400 400 250250 200 500 500 200 Depth (H) 42 42 23 38 49 35 21 42 42 100 P/H 11.911.9 17.4 10.5 5.1 5.7 9.5 11.9 11.9 2.0 Coating V 500 350 500 500 500500 100 300 100 500 Velocity Silver Nanowire 90 90 90 90 90 70 40 90 9085 Layer Thickness Film Substrate PC COP COP COP COP COP COP COP COP COPResistance MD 86.6 80.7 121.3 95.0 56.7 99.2 219.6 79.4 95.2 80.1 ValueTD 81.7 104.1 138.2 104.8 84.1 147.9 349.9 110.8 139.9 144.2 TD/MD 0.941.29 1.14 1.10 1.48 1.49 1.59 1.38 1.47 1.80 Sheet Resistance 40 36 5045 29 54 189 40 47 38 Total Light 89 90 90 90 90 90 90 90 90 90Transmittance Haze 0.93 0.82 0.72 0.78 1.17 0.57 0.33 0.78 0.54 0.84

As shown in Table 1, regardless of the bar groove shape and the coatingvelocity V, in Example 1 to Example 19 in each of which the pitch(P)/depth (H)[P/H] is 5 or more, the in-plane resistance anisotropy((R_(TD))/(R_(MD))) of the conducting layer is smaller, compared to thecase where an ordinary Meyer bar (or wire bar) was used (ComparativeExample 1). Further, when the bar groove shape satisfied the pitch(P)/depth (H)[P/H] of 9 or more, and the coating velocity V was 350mm/sec or more, (R_(TD))/(R_(MD)) became a preferable result of 0.7 to1.3, and a transparent conducting film having almost no in-planeresistance anisotropy could be obtained. The reason therefor is assumedthat when the bar groove shape satisfies a pitch (P)/depth (H)[P/H] of apredetermined value or higher, a phenomenon that the silver nanowire inkeasily flows in the lateral direction is induced, and thereby, thedirections of the metal nanowires can be made uniform in the printingdirection and the direction perpendicular to the printing direction.Further, when the coating velocity is higher, the silver nanowire inkitself flows at a higher speed, which induces the phenomenon that thesilver nanowire ink easily flows in the lateral direction. Then, same asabove, the directions of the metal nanowires can be made uniform.Accordingly, when printing conditions satisfying both of them areadopted, a transparent conducting film having almost no in-planeresistance anisotropy within a plane can be produced.

Further, even if the bar groove shapes were different, as far as thepitch (P)/depth (H)[P/H] ratio was within a specific range, atransparent conducting film having almost no in-plane resistanceanisotropy could be produced. Further, without changing the silvernanowire concentration, the sheet resistance value could be adjusted bychanging the bar groove shape.

On the other hand, when the bar shape had a pitch (P)/depth (H) of lessthan 9, or the coating velocity was less than 350 mm/sec, the in-planeresistance anisotropy ((R_(TD))/(R_(MD))) exceeded 1.3. In both cases,flows of the silver nanowire ink in the lateral direction were induced,but slightly weak. Namely, it is assumed that when only the bar shapehad a pitch (P)/depth (H) of 9 or more, or when only the coatingvelocity was high, although flows of the silver nanowire ink in thelateral direction were induced, the flows were not strong enough touniform the directions of the metal nanowires.

The Meyer bar (or wire bar) used in the Comparative Example 1 wasproduced by winding a wire having a diameter D around a bar, and thus,the pitch (P)/depth (H)=D/(D/2)=2. Therefore, even if the thickness ofthe wire is changed, the ratio is constant. It is assumed that this isthe reason why the in-plane resistance anisotropy was large.

Example 20

Except that a wireless bar OSP-CN-22L (bar groove shape: S-shape/pitch(P): 500 μm, depth (H): 42 μm, P/H: 11.9, bar surface: Diamond-LikeCarbon (friction coefficient: 0.15), manufactured by Cotec Corporation),only the surface material of which is different from the bar used inExample 1, was used, other conditions were the same as those ofExample 1. The results are shown in Table 2.

Example 21

Except that a coating velocity V of the silver nanowire ink was 300mm/sec, other conditions were the same as those of Example 20. Theresults are shown in Table 2.

Example 22

Except that a coating velocity V of the silver nanowire ink was 100mm/sec, other conditions were the same as those of Example 20. Theresults are shown in Table 2.

Example 23

Except that PET (untreated surface of COSMOSHINE (registered trademark)A4100, manufactured by Toyobo Co., Ltd.) was used as a transparentsubstrate, other conditions were the same as those of Example 20. Theresults are shown in Table 2.

Example 24

Except that a wireless bar OSP-CN-22L (bar groove shape: S-shape/pitch(P): 500 μm, depth (H): 42 μm, P/H: 11.9, bar surface: SUS304 (frictioncoefficient: 0.45), manufactured by Cotec Corporation) was used, otherconditions were the same as those of Example 20. The results are shownin Table 2.

Example 25

Except that a wireless bar OSP-CN-22L (bar groove shape: S-shape/pitch(P): 500 μm, depth (H): 42 μm, P/H: 11.9, bar surface: hard chromeplating (friction coefficient: 0.70), manufactured by Cotec Corporation)was used, other conditions were the same as those of Example 20. Theresults are shown in Table 2.

Comparative Example 2

Except that a wire bar #8 (using wire of ΦD=200 μm, wire surface: SUS304(friction coefficient: 0.45)) was used, other conditions were the sameas those of Example 20. The results are shown in Table 2. Because thebar used was different from the bar used in Example 20, the resultingsilver nanowire layer had a thickness smaller than that of Example 20.

TABLE 2 Unit Ex. 20 Ex. 21 Ex. 22 Ex. 23 Ex. 24 Ex. 25 Com. Ex. 2 SilverNanowire Average Diameter nm 26 26 26 26 26 26 26 Silver NanowireAverage Length μm 20 20 20 20 20 20 20 Ink Silver Concentration mass %0.17 0.17 0.17 0.17 0.17 0.17 0.17 Binder Resin PNVA PNVA PNVA PNVA PNVAPNVA PNVA Ink Viscosity mPa · s 4.1 4.1 4.1 4.1 4.1 4.1 4.1 (25° C.) BarShape Shape S S S S S S — Pitch (P) μm 500 500 500 500 500 500 200 Depth(H) μm 42 42 42 42 42 42 100 P/H 11.9 11.9 11.9 11.9 11.9 11.9 2.0 BarSurface Diamond-Like (Friction 0.15 0.15 0.15 0.15 Carbon Coefficient)SUS304 0.45 0.45 Hard Chrome 0.70 Plating Coating V mm/sec 500 300 100100 100 100 100 Velocity Silver Nanowire Layer Thickness nm 90 90 90 9090 90 85 Transparent Substrate COP COP COP PET COP COP COP Resistance MDΩ 79.6 86.5 75.0 82.0 75.1 72.7 92.8 Value R TD Ω 85.2 83.7 69.7 90.3107.0 107.6 165.5 TD/MD 1.07 0.97 0.93 1.10 1.42 1.48 1.78 SheetResistance Ω/□ 36 35 36 36 46 38 70 Total Light Transmittance % 90 90 9090 90 90 90 Haze % 1.04 0.91 1.07 1.46 0.83 0.97 0.68

As shown in Table 2, regardless of the bar surface material (frictioncoefficient) and the coating velocity V, in Example 20 to Example 25 ineach of which the pitch (P)/depth (H)[P/H] is 5 or more, and preferably9 or more, the in-plane resistance anisotropy of the conducting layer issmaller, compared to the case where an ordinary Mayer bar (or wire bar)was used (Comparative Example 2). Further, in Example 20 to Example 23in each of which a wireless bar having a bar groove shape satisfying apitch (P)/depth (H)[P/H] of 9 or more and having a bar surface with afriction coefficient of 0.15 was used, (R_(TD))/(R_(MD)) became apreferable result of 1.3 or less, and a transparent conducting filmhaving a small in-plane resistance anisotropy could be obtained. Thereason therefor is assumed that when the bar groove satisfies a pitch(P)/depth (H)[P/H] of 9 or higher, a phenomenon that the silver nanowireink easily flows in the lateral direction (the direction (TD)perpendicular to the printing direction in FIG. 2A) was induced, andorientation of the metal nanowires in the printing direction wasdecreased, resulting in making the directions of the metal nanowirescloser to random. Further, it is assumed that when the bar surface has asmall friction coefficient, the phenomenon that the silver nanowire inkeasily flows in the lateral direction is further induced, the resultingin making the directions of the metal nanowires further closer torandom. Accordingly, when printing conditions satisfying both of themare adopted, a transparent conducting film having almost no in-planeresistance anisotropy can be produced.

On the other hand, when the coating velocity was less than 350 mm/sec(V: 100 mm/sec), even if the bar shape had a pitch (P)/depth (H) of 9 ormore, Examples having the bar surface friction coefficient of more than0.40, i.e., Example 24 (bar surface friction coefficient: 0.45) and inExample 25 (bar surface friction coefficient: 0.70), showed the in-planeresistance anisotropy ((R_(TD))/(R_(MD))) exceeded 1.3. In these cases,flows of the silver nanowire ink in the lateral direction were induced,but slightly weak. Further, in Comparative Example 2 where a Meyer bar(or wire bar) having a bar surface friction coefficient of 0.45, andhaving a pitch (P)/depth (H)[P/H] corresponding to 2 was used, thein-plane resistance anisotropy ((R_(TD))/(R_(MD))) was 1.78, which wasvery high.

Therefore, by a method for producing a transparent conducting filmaccording to the present disclosure in which bar-coat printing isperformed using a bar provided on the surface thereof with a grooveadjusted into a specific shape, a transparent conducting film having asmall in-plane resistance anisotropy can be obtained.

The invention claimed is:
 1. A method for producing a transparentconducting film provided with a conducting layer containing metalnanowires and a binder resin, comprising steps of: preparing a coatingliquid containing the metal nanowire and the binder resin, and coatingthe coating liquid on one main face of a transparent substrate, wherein,in the coating step, a bar-coat printing method is performed using a barprovided with a groove having a pitch (P) and a depth (H) which satisfya ratio P/H of 5 to 30, and wherein a ratio (R_(TD)/R_(MD)) of aresistance value of the conducting layer in a direction perpendicular toan in-plane coating direction of the coating liquid (R_(TD)) to aresistance value of the conducting layer in the in-plane coatingdirection of the coating liquid (R_(MD)) is 0.93 to 1.59.
 2. The methodfor producing a transparent conducting film according to claim 1,wherein a material forming a surface of the bar has a frictioncoefficient of 0.05 to 0.45.
 3. The method for producing a transparentconducting film according to claim 2, wherein, when the coating liquidis coated on one main face of the transparent substrate, a relativemoving velocity (coating velocity) V (mm/sec) of the transparentsubstrate relative to the bar satisfies 2000≥V≥350.
 4. The method forproducing a transparent conducting film according claim 3, wherein whenthe groove formed on the bar has a pitch (P) and a depth (H), a ratioP/H is 9 to
 30. 5. The method for producing a transparent conductingfilm according to claim 2, wherein when the groove formed on the bar hasa pitch (P) and a depth (H), a ratio P/H is 9 to
 30. 6. The method forproducing a transparent conducting film according to claim 1, wherein amaterial forming a surface of the bar has a friction coefficient of 0.05to 0.40.
 7. The method for producing a transparent conducting filmaccording to claim 6, wherein, when the coating liquid is coated on onemain face of the transparent substrate, a relative moving velocity(coating velocity) V (mm/sec) of the transparent substrate relative tothe bar satisfies 2000≥V≥50.
 8. The method for producing a transparentconducting film according to claim 7, wherein when the groove formed onthe bar has a pitch (P) and a depth (H), a ratio P/H is 9 to
 30. 9. Themethod for producing a transparent conducting film according to claim 6,wherein when the groove formed on the bar has a pitch (P) and a depth(H), a ratio P/H is 9 to
 30. 10. The method for producing a transparentconducting film according to claim 1, wherein when the groove formed onthe bar has a pitch (P) and a depth (H), a ratio P/H is 9 to
 30. 11. Themethod for producing a transparent conducting film according to claim 1,wherein the metal nanowires have an average length of 1 to 100 μm and anaverage diameter of 1 to 500 nm.
 12. The method for producing atransparent conducting film according to claim 1, wherein the coatingliquid has a viscosity in a range of 1 to 50 mPa·s.
 13. The method forproducing a transparent conducting film according to claim 1, whereinthe metal nanowire has an average diameter size of 5 to 100 nm, anaverage major axis length of 2 to 70 μm, and an average aspect ratio 100or more.